F.5

The Hiro Naval Arsenal F.5 was a Japanese experimental fighter developed in the early 1930s to meet the Imperial Navy’s demand for a high‑performance interceptor. Designed by the Hiro team under the direction of naval engineer Kiyoshi Matsuo, the prototype first flew on 12 April 1933 at the Kasumigaura airfield. Unlike contemporary biplanes, the F.5 featured an all‑metal low‑wing monoplane layout, retractable landing gear, and an enclosed cockpit that reduced drag and improved pilot comfort. Power was supplied by a 775‑horsepower Nakajima Ha‑5 radial engine driving a two‑bladed propeller, granting a maximum speed of 470 km/h and a service ceiling of 9,500 meters. The aircraft incorporated leading‑edge slats and split‑type flaps, providing superior low‑speed handling during carrier landings. Although only a handful of prototypes were built before the program was cancelled in favor of the Mitsubishi Ka‑14, the F.5’s advanced construction techniques influenced later Japanese designs, especially the emphasis on all‑metal airframes and retractable gear. Its brief existence demonstrated the navy’s willingness to experiment with modern aerodynamics, marking a transitional step from biplane fighters to the sleek monoplane era that dominated World War II aviation.

Hiro Naval Arsenal

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Design & Classification